Abstract: As an advanced plastic processing technology, forging rolling technology which is consist of hot forging process and radial hot ring rolling process is widely used in the production of small and medium size bearing rings. During the process, sunking defect is easy formed in outer diameter of ring’s upper and lower surface’s edge. This will increase machining allowance, reduce material utilization and even may lead the ring scrapped. In view of the problem, a whole forging rolling process model of GCr15 bearing ring is established under Transvalor. Forge software environment. The model not only directly reflects evolution process of bearing ring’s sunking defect but also reveals the forming mechanism and the rule of evolvement. The impact of hot forging’s upsetting radio, hot rolling’s feed speed, hot rolling’s friction coefficient and hot rolling’s initial temperature on the sunking defect of bearing ring are studied. The results show that the sunking defect is more greatly affected by hot forging’s upsetting radio，hot rolling’s feed speed and hot rolling’s friction coefficient than by hot rolling’s initial temperature. These will provide a scientific guidance for control the sunking defect in forging rolling process of bearing ring, through the study of the evolution behavior of sunking defect in forging rolling process of GCr15 bearing ring.

Key words: sunking defect;bearing ring;forging and rolling process;numerical simulation